This invention relates generally to antenna systems and more particularly to phased array antenna systems.
As is known in the art, an array antenna includes a plurality of individually radiating elements. Each of such elements are typically independently controlled to radiate a electromagnetic signal having a selected relative phase relationship to the other ones of the microwave signals. The relative phase of each of the microwave signals, therefore, is controlled to obtain a desired radiation pattern. The pattern obtained is the result of the combined action of all the individual transceiver and radiating elements. Several techniques exist for providing the desired control of the individual radiating elements to achieve the desired radiation pattern. In general, a phase shifter is disposed to provide the selected phase shift characteristic. Generally, in more sophisticated phased array radar systems, the phase shifter is included as part of a transceiver circuit or module. A transceiver circuit or module has the capability of providing a transmit and a receive path in which the phase of the module can be controlled.
Several techniques exist for providing so-called transceiver modules. In general, the transceiver module includes a low noise amplifier for the receive mode, a power amplifier for the transmit mode, and a pair of single pole double-throw switches. Branch ports of each of the switches are coupled to an input and an output of each one of the amplifiers. This arrangement is then coupled to a reciprocal phase shifter. Thus such a transceiver includes a pair of amplifiers, each disposed in one of the pair of signal paths which are both coupled to a reciprocal phase shifter. Although useful for many applications, this transceiver architecture is not desirable for jamming monopulse radars because of the large differences in insertion phase which exist between the distinct signal paths, particularly due to the separate transmit and receive amplifiers.
An alternative arrangement is to provide a common signal path through which both transmit and receive signals pass through a phase shifter and amplifier. Although this architecture provides a common signal path for both transmit and receive signals obviating the problem of insertion phase, this advantage is achieved at the cost of two additional transmit receive switches. One of these transmit receive switches is connected in series between the signal path and the antenna element. Accordingly, the output signal from the amplifier during transmit will always be attenuated by the presence of two series switches, thus causing a relatively poor efficiency for the transceiver module. In some applications this is tolerable but in other applications it is undesirable.
A further problem with each of these techniques is that it is most desirable to provide a transceiver module architecture on a single monolithic microwave integrated circuit. The general trend in microwave technology particularly as it relates to phased array elements is to form these circuits on a single integrated circuit using monolithic microwave integrated circuit techniques. Thus, any architecture which increases the number of components provides a concomitant reduction in the ability to successfully integrate the transmit/receive function as a single integrated circuit with acceptable yields and cost.